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Related Concept Videos

Mass Spectrometry: Molecular Fragmentation Overview01:20

Mass Spectrometry: Molecular Fragmentation Overview

The ionization of a molecule into a molecular ion inside the mass spectrometer causes instability in the molecule's structure due to the loss of an electron. This eventually leads to the fragmentation or breaking of some bonds in the molecule. The fragmentation occurs predominantly at specific bonds to yield relatively stable fragments.
One type of fragmentation pattern is the cleavage of a single bond in the molecular ion. The cleavage leads to a radical and a cation. The cleavage can occur at...
Mass Spectrometry: Alcohol Fragmentation01:03

Mass Spectrometry: Alcohol Fragmentation

Alcohols (R-OH) ionize to lose one non-bonded electron from the oxygen atom, forming molecular ions. Due to their tendency to fragment rapidly, the intensity of the molecular ion peak in the mass spectrum is weak or sometimes absent. The fragmentation patterns for alcohols occur in two ways, i.e. ⍺-cleavage and dehydration. During ⍺-cleavage, the bond at the ⍺-position adjacent to the hydroxyl group cleaves to give a resonance-stabilized cation and a radical. However, intramolecular dehydration...
Mass Spectrometry: Carboxylic Acid, Ester, and Amide Fragmentation01:01

Mass Spectrometry: Carboxylic Acid, Ester, and Amide Fragmentation

The fragmentation patterns observed for compounds such as carboxylic acids, esters, and amides in the mass spectra include ⍺-cleavage and McLafferty rearrangement. Fragmentation by ⍺-cleavage preferentially occurs at the carbon-carbon bond at the ⍺-position next to the carboxylic group to generate a neutral radical and a cation. Long chain compounds with hydrogen at their γ-carbon undergo McLafferty rearrangement to give a radical cation and a neutral alkene.
For example, the fragmentation of...
X-ray Crystallography02:18

X-ray Crystallography

The size of the unit cell and the arrangement of atoms in a crystal may be determined from measurements of the diffraction of X-rays by the crystal, termed X-ray crystallography.
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...
Phase Transitions: Melting and Freezing02:39

Phase Transitions: Melting and Freezing

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
Crystal Field Theory - Octahedral Complexes02:58

Crystal Field Theory - Octahedral Complexes

Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...

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Related Experiment Video

Updated: May 30, 2026

Spatial Separation of Molecular Conformers and Clusters
10:37

Spatial Separation of Molecular Conformers and Clusters

Published on: January 9, 2014

Sonofragmentation of molecular crystals.

Brad W Zeiger1, Kenneth S Suslick

  • 1Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.

Journal of the American Chemical Society
|August 26, 2011
PubMed
Summary

High-intensity ultrasound breaks molecular crystals like aspirin. Experiments show particle collisions are not the cause; direct shock wave interactions are the primary mechanism for sonofragmentation.

Area of Science:

  • Crystallography
  • Physical Chemistry
  • Materials Science

Background:

  • Molecular crystals are crucial in pharmaceuticals, but their mechanical properties under stress are not fully understood.
  • High-intensity ultrasound is used in pharmaceutical processing, yet the precise fragmentation mechanisms remain unclear.

Purpose of the Study:

  • To investigate the primary mechanisms responsible for the sonofragmentation of molecular crystals.
  • To elucidate the role of different collision types in crystal breakage under ultrasonic conditions.

Main Methods:

  • Utilized acetylsalicylic acid (aspirin) crystals as a model for active pharmaceutical ingredients.
  • Conducted kinetics experiments to assess particle-particle collision contributions.
  • Performed decoupling experiments to differentiate between particle-horn and particle-wall interactions.

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On-Chip Crystallization and Large-Scale Serial Diffraction at Room Temperature

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Last Updated: May 30, 2026

Spatial Separation of Molecular Conformers and Clusters
10:37

Spatial Separation of Molecular Conformers and Clusters

Published on: January 9, 2014

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
06:44

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding

Published on: March 24, 2018

On-Chip Crystallization and Large-Scale Serial Diffraction at Room Temperature
07:42

On-Chip Crystallization and Large-Scale Serial Diffraction at Room Temperature

Published on: March 11, 2022

Main Results:

  • Kinetics studies definitively ruled out particle-particle collisions as a mechanism for sonofragmentation.
  • Decoupling experiments demonstrated that particle-horn and particle-wall collisions are not the dominant fragmentation pathways.
  • Evidence strongly supports direct particle-shock wave interactions as the principal cause of crystal breakage.

Conclusions:

  • Sonofragmentation of molecular crystals is primarily driven by direct interactions with shock waves generated by ultrasound.
  • Understanding this mechanism is critical for optimizing ultrasonic processing in pharmaceutical ingredient manufacturing.
  • This study clarifies a key physical process in the application of ultrasound to crystalline materials.